Abrading device



United States Patent 3,098,339 ABRADING DEVICE Dirck J. Olton,Loutlonville, N.Y., and Russell P. Hook, Sutton, Mass, assignors toNorton Company, Worcester, Mass, a corporation of Massachusetts FiledNov. 22, 1961, Ser. No. 154,149 6 Claims. (Cl. 51-197) The inventionrelates to an abrading or lapping device, and more particularly to animprovement for abrading or lapping devices comprising means forsupporting and uniformly tensioning a sheet of abrading material uponthe rotatable lapping head or plate of a lapping machine or otherapparatus for abrading a work piece.

Due to the fact that certain abrading operations and particularlylapping operations remove only a very small amount of material from thesurface of a work piece bemg abraded or lapped, sheet material with anabrasive surface such as that commonly known as a coated abrasive sheetmay be used for certain abrading or lapping operations in place of arelatively more expensive solid abrasive lap of the type well known inthe art with the additional advantage that sheets of abradant ofdifferent grades are readily changeable as required and the furtheradvantage that the normal requirement for truing a solid abrasive lapperiodically is eliminated simply by the replacement of a worn sheet ofabradant with a new sheet of abradant as required. Moreover, replacementsheets of abradant may be stored in less space and may be handled morereadily than solid abrasive laps of substantial thickness and verysubstantial weight.

While it is well known in many applications to secure sheets of abradantsuch as coated abrasive sheets to backing surfaces by means of suitableadhesives in order to properly secure the sheet material, thesubstitution of a new sheet of abradant for a worn sheet or a sheet of adifferent grade is rendered more difficult by the fact that the sheet tobe replaced is secured by an adhesive and it is extremely difficult tobe certain that the layer of adhesive by means of which the new sheet issecured is of uniform thickness throughout the entire area of the sheetsecured thereby.

In contrast to the prior art teachings, the instant inventioncontemplates an arrangement for supporting and tensioning a sheet ofabradant adjacent to a suitable supporting surface so that the propercontour of a sheet of abradant is assured by its direct engagement overits entire area with a precisely formed supporting surface and so that asheet of abradant may be released from the supporting surface simply byreleasing the tensioning means therefor in the absence of an adhesivecoating between the sheet of abradant and the supporting surface.

One example of a machine to which the present invention could be appliedis illustrated in US. Patent 2,695,479 to Herbert S. Indge showing alapping machine in which the abrasive lap could be replaced by a metallap with a suitable surface for supporting a sheet of abradantadditionally provided with means for clamping and radially tensioning asheet of abradant as described below and illustrated in the accompaniyngdrawing.

It is therefore one object of the invention to provide an abradingdevice for use on abrading machines such as lapping machines or the likewhereby abrasive sheets may be supported and secured for use inperforming abrading or lapping operations.

Another object of the invention is to provide an abrading devicecomprising an attachment for abrading machines such as lapping machinesoperable to uniformly tension a sheet of abradant supported inengagement with a suitable supporting surface therefor.

Still another object is to provide an abrading device for supporting anduniformly tensioning a sheet of abradant including a plurality ofcoating tensioning. devices operable in unison.

A further object is to provide an abrading device for supporting anduniformly tensioning a sheet of abrasive releasable for the insertion ofsheets of abradant of different grades as required.

Other objects and advantages of the instant invention will becomeapparent from consideration of the following description and from theshowing in the accompanying drawing wherein:

FIG. 1 is a plan view of the preferred embodiment of the abrading devicewith a sheet of abr-adant supported and uniformly tensioned thereon, and

FIG. 2 is a sectional view through the preferred embodiment of theabrading device taken approximately on line 22 of FIG. 1 showing thisdevice as it would appear when incorporated on :a conventional lappingmachine, with portions of such a lapping machine indicated in FIG. 2 byphantom lines.

As illustrated in the drawing, the abrading or lapping device preferablycomprises a circular backing plate or lap 1E arranged to be mounted upona support rotatable about a vertical axis such as that provided in aconventional lapping machine. Reference may be had to US. Patent2,695,479 referred to above for additional details of a lapping machineof the general type to which this invention may be applied.

The backing plate or lap 16 may be, but is not necessarily, providedwith a central hole 12 therethrough, its configuration in this respectgenerally depending upon the configuration of the lapping machine onwhich it is mounted.

As shown in FIGS. 1 and 2, the backing plate 10 is provided with :aplurality of spaced parallel guides 13 and 13a which may be secured tothe backing plate 10 by threadable engagement therewith as shown in thedrawing. Each pair of guides 13 and 13a supports one of a plurality ofradially movable segmental members 20 each provided with a pair ofparallel holes for this purpose. Each pair of guides 13 and 13aprecludes angular displacement of the movable member 20 supportedthereby relative to the backing plate 10 and limits radial movement ofthe associated movable member 20 by a suitable limit stop such as thestop nuts 14 illustrated in the drawing.

The backing plate 19 is also provided with a circumferential supportcomprising a tongue 15 extending around the periphery of the backingplate 10* as shown in the drawing which may be either secured to orformed integrally with the backing plate 10. Each of the movable members29 is provided with an inwardly opening slot or groove 17 with opposedsurfaces mating with the opposed surfaces 16 and 16a of the tongue 15for sliding engagement therewith. The circumferential support comprisingtongue 15 thus provides a common supporting means for the respectivemembers 2! restraining the respective members 29 against verticalmovement with the upper surfaces of the respective members positionedcoplanar with the upper surface of the backing plate 10 while permittingradial movement of the respective movable members Ztl along therespective pairs of guides 13 and 13a. As noted above, the amount ofradial movement of the respective members 20 is limited by therespective nuts 14- threadably engaging and thereby adjustable on therespective guides 13a.

Each of the movable members 29 is provided with at least one pair ofoppositely sloped cam engaging or following surfaces 22. As illustratedin FIG. 1, each member 20 is provided with two pairs of such camengaging surfaces. Precise coplanar alignment between the top surface 26of the backing plate 10' and the flat planar upper surfaces 24 of therespective movable members can be assured by machining all of thesurfaces 24 and the surface 26' simultaneously after the respectivemembers 20 have been assembled on the backing plate 10. In this manner,this device is provided with an uninterrupted flat surface for properlysupporting a sheet of abradant material 28.

Each of the movable members 20 is provided with a clamping element 30for engaging the outer edge portion of a sheet of abradant material,each releasably secured to the associated movable member 20 by aplurality of screws 32 and washers 34 disposed as shown best in FIG. 2with the screws 32 extending through elongated slots 36 in each clampingelement 30 and threadably engaging suitable holes in the respectivemembers 20.

In the embodiment of the instant invention illustrated in the drawing,the backing plate 10 is shown as comprising an annular ring with acentral opening therethrough. Accordingly, a clamping ring 38 isprovided for securing the inner edge of the sheet of abradant materialto the backing plate 10 by means of a plurality of screws 40 threadablyengaging the backing plate 10. In applications where the backing plate10 comprises an uninterrupted circular disc, the sheet of abradant neednot be provided with a central opening therethrough. Hence the clampingring 38 and the attachment screws 40 therefor could be eliminatedwithout affecting the function of the tensioning means described below.

A unitary rotatably mounted camming member 44 having a central opening46 therethrough is fitted into an annular recess 48 formed adjacent tothe periphery of the backing plate 10 and provided with a shoulder 50engaging the surface of the opening 46 in the annular member 44 so thatthe member 44 is maintained con centric of the backing plate 10.

The member 44 is maintained in operative relation to the backing plate10 by an annular ring 52 secured to the backing plate 10 by a pluralityof screws 53 and forming the upper wall of the recess 48. The uppersurface 54 of the annular ring 52 is coplanar with and in fact forms anextension of the supporting surface 26 of the backing plate 10 and aprecise coplanar relationship is conveniently established by a grindingor other machining operation after the annular ring 52 is secured to thebacking plate 10, preferably by the machining operation referred toabove for establishing the proper relationship between the surface 26and the upper surfaces 24 of the respective members 20.

The rotatable member 44 is provided along its outer periphery with aplurality of spaced pairs of camming surfaces 56 disposed for engagementwith the respective pairs of cam engaging surfaces 22 provided on theradial- 'ly movable members 20. With this arrangement, rotation of therotatable member 44 in either direction relative to the backing plate 10produces sliding movement of the respective members 20 radiallyoutwardly of the backing plate 10 in unison.

A means for rotating the camming member 44 in either direction is alsomounted within or supported by the backing plate 10. As illustrated inFIGS. 1 and 2, the means for rotating the member 44 comprises a shortsection of gear teeth 58 formed along the inner surface 46 of thecamming member 44, a pinion 60 meshing with the gear teeth 58 andmounted on a shaft 62 which may be journal-led in the backing plate 10,a worm gear 64 secured to the lower end of shaft 62 within an opening 66in the backing plate 10, a worm 68 secured to a rotaable shaft 70, alsojournalled in the backing plate 10, and disposed in engagement with theworm gear 64, and a shaped head 72 provided on the outer end of shaft 70for engagement with a suitable crank or wrench operable to rotate theshaft 70 and thereby the rotatable camming member 44, through theinterconnected driving elements described above collectively comprisinga unidirectional drive operable in either direction in response torotation of the shaft 70.

Operation of the device comprising the instant invention first requiresrotation of the shaft 70 to rotate the worm 68, the Worm gear 64, theshaft 62, the gear 60 and the rotatable member 44 so that the cammingsur faces 56 are not biased into engagement with the cam engagingsurfaces 22. If there is a sheet of abradant material 28 installed onthis device, such rotation of the rotatable member 44 is effective torelease all of the tension applied to the sheet of abradant material andto allow the respective movable members 20 to return to their originalinnermost positions. The respective screws 32 are loosened so that theclamping elements 30 may be moved outwardly relative to the respectivemovable members 20 the length of the elongated slots 36 through theclamping elements 30 in order to clear the outer edge of the sheet ofabradant. In embodiments of the instant invention in which the sheet ofabradant material 28 is provided with a central opening as shown in thedrawing, the clamping ring 38 is released by removing the screws 40, andthen removed from the backing plate 10.

A sheet of abradant material 28 supported upon the upper surface 26 ofthe backing plate 10 can now be removed and replaced with another sheetof abradant material 28. The replacement sheet of abradant material 28is then deposited upon the upper surface 26 of the backing plate *1!)with its central opening, if any, concentric of the central hole :12 ofthe backing plate 10. In embodiments of the instant invention whereinthe backing plate 10 comprises an uninterrupted circular disc, a sheetof abradant material 28 without a central opening therethrough may bepositioned concentric of the movable segments 20.

In embodiments of the instant invention wherein the clamping ring 38 isused, this ring is then replaced and secured to the backing plate '10 bythe screws 40 in order to clamp the inner edge portion of an annularsheet of abradant material 28 to the annular backing plate 10. Next,each of the clamping elements 30 is then moved inwardly individually thelength of the elongated slots 36 so that it is disposed over a portionof the outer edge of the sheet of abradant material 28. With eachclamping element 30 so disposed and with its associated movable member20 held against the periphery of the backing plate .10, the clampingscrews 32 for that clamping element are tightened to clamp the outeredge portion of the sheet of abradant material 28 to each of the movablemembers 20.

When all of the clamping elements 30 have been secured in the mannerdescribed above, a wrench or crank engaging the head 72 on the shaft 70is turned in either direction to rotate the worm 68, the worm gear 64,the gear 60 and thence the rotatable camming member 44 in order to biasthe respective camming surfaces 56 into engagement with the associatedcam engaging surfaces 22 on all of the movable members '20 in order tomove all of the slidably movable members 20 outwardly equal amountsrelative to the backing plate 10 in unison so that the sheet of abradantmaterial 28 is uniformly tensioned over its entire working surface. Therespective movable members 20 are maintained in fixed angularrelationship to the backing plate r10 during this radial movement by therespective pairs of parallel guides 13 and 13a engaging these movablemembers.

In use the abrading device of the instant invention can be mounted on alapping machine as shown in phantom lines in FIG. 2 of the drawing,wherein the various elements so illustrated correspond to variouselements of the lapping machine illustrated in US. Patent 2,695,479referred to above to which reference may be had for additional detailsnot illustrated in FIG. 2. As shown in FIG. 2, the backing plate 10 issecured to and rotatable with a member supported by a suitable base notshown for rotation in a predetermined direction about a first verticalaxis. A rotatable cage 82 with apertures therethrough for receiving aplurality of work pieces W is rotatably supported in a plane parallel toand a predetermined distance above the surface of the abradant material28 upon a bushing 84 adjustably secured to a stationary shaft 86 whichmay be disposed on a second vertical axis. While the first and secondvertical axes referred to above may be coincident as suggested by theshowing in FIG. 1, they may alternatively be offset so that the cage 82is disposed eccentric of the base plate in the manner illustrated anddescribed in detail in U.S. Patent 2,695,479. The cage 82. mayconveniently be rotated by driving elements engaging a gear 88 on theouter periphery of the cage 82. Where necessary, Weights may be appliedto the upper surfaces of the work pieces W by any suitable arrangementsuch as that illustrated in Patent 2,695,479 in order to enhance theabrading operation.

It will be seen that there has been provided by this invention apparatusin which the objects hereinabove set forth together with many thoroughlypractical advantages are successfully achieved. As many possibleembodiments and changes may be made of the instant invention, it is tobe understood that all matter hereinbefore set forth or shown in theaccompanying drawing is to be interpreted as illustrative rather than ina limiting sense.

What is claimed is:

1. An abrading device comprising, a backing plate, supporting meansdisposed adjacent the perimeter of said backing plate, a plurality ofmembers supported by and outwardly movable on said supporting means, asheet of abradant supported by said backing plate, means to clamp saidsheet of abradant to each of said movable members, and means mountedadjacent said backing plate operable to move all of said movable membersoutwardly in unison by coordinated amounts to uniformly tension saidsheet of abradant.

2. An abrading device comprising, a backing plate, a supporting meansincluding a continuous tongue extending outwardly from and disposedaround said backing plate, a plurality of outwardly movable memberssupported on said supporting means, all of said outwardly movablemembers being provided with cam engaging surfaces, a sheet of abradantsupported on said packing plate, means to clamp said sheet of abradantto each of said outwardly movable members, and means mounted upon saidbacking plate including a rotatable member with cam surfaces operable tomove all of said movable members outwardly in unison by coordinatedamounts to uniformly tension said sheet of abradant.

'3. An abrading device comprising, a circular backing plate, asupporting means disposed around and extending outwardly from saidbacking plate, a plurality of radially movable members mounted on saidsupporting means, all of said movable members being provided with camengaging surfaces, a circular sheet of abradant with a central holetherethrough supported on said backing plate, means to clamp the inneredge of said sheet of abradant to said backing plate, means to clampsaid sheet of abradant to each of said movable members adjacent theouter edge thereof, and means mounted upon said backing plate operableto move all of said movable members outwardly an equal amount in unisonto uniformly tension said sheet of abradant.

4. An abrading device comprising, a circular backing plate, a circularsupport disposed about the periphery of the backing plate, a pluralityof spaced parallel pairs of elongated guide means extending outwardlyfrom said backing plate, a plurality of radially movable membersrespectively supported in sliding engagement with the respective pairsof guide means and in mating engagement with said circular support, allof said radially movable members being provided with cam engagingsurfaces, a sheet of abradant supported on said backing plate, means toclamp said sheet of abradant to each of said radially movable members,rotatable means mounted adjacent said backing plate including spacedcamming surfaces operable against the respective cam engaging sur facesto move all of said movable members outwardly an equal amount in unisonto uniformly tension said sheet of abradant.

5. An abrading device comprising, a backing plate, a projecting tonguedisposed around the perimeter of said backing plate, a plurality ofguide means extending outwardly from and spaced around said backingplate, a plurality of members mounted slidably on said guide means eachhaving a groove disposed in mating engagement with said tongue, all ofsaid movable members being provided with identical cam engagingsurfaces, a sheet of abradant on said backing plate, means to clamp saidsheet of abradant to each of said slidable members, a unitary cammingmeans rotatably mounted within said backing plate and disposed forengagement with the respective cam engaging surfaces to move all of saidslidable members outwardly equal amounts in unison to uniformly tensionsaid sheet of abradant, and means including a rotatable worm and wormgear housed in said backing plate operable to rotate said unitarycamming means.

6. An abra'ding device comprising, a circular backing plate, asupporting means projecting from the circumference of said backingplate, spaced pairs of parallel guide means extending outwardly fromsaid backing plate, a segment slidably movable on each pair of parallelguide means and disposed in engagement with said continuous guide, allof said slidably movable segments being provided with identical camengaging surfaces, a sheet of abradant supported upon said backingplate, means to clamp said sheet of abradant to each of said slidablymovable segments, a unitary circular member rotatably mounted upon saidbacking plate having a plurality of spaced cams on the periphery thereoffor engaging all of the cam engaging surfaces on the respective slidablymovable segments, rotating means engaging a coacting surface of saidunitary circular member, a rotatable worm and worm gear mechanismmounted in said backing plate for rotating said rotating means, and saidunitary circular member to move all of said slidably movable segments anequal amount in unison to uniformly tension said sheet of abradant.

References Cited in the file of this patent UNITED STATES PATENTS905,464 Sadler Dec. 1, 1908

1. AN ABRADING DEVICE COMPRISING, A BACKING PLATE, SUPPORTING MEANDDISPOSED ADJACENT THE PERIMETER OF SAID BACKING PLATE, A PLURALITY OFMEMBERS SUPPORTED BY MEANS AND OUTWARDLY MOVABLE ON SAID SUPPORTINGMEANS, A SHEET OF ABRADANT SUPPORTED BY SAID BACKING PLATE, MEANS TOCLAMP SAID SHEET OF ABRADANT TO EACH OF SAID MOVABLE MEMBERS, AND MEANSMOUNTED ADJACENT SAID BACKING PLATE OPERABLE TO MOVE ALL OF SAID MOVABLEMEMBERS OUTWARDLY IN UNISON BY COORDINATED AMOUNTS TO UNIFORMLY TENSIONSAID SHEET OF ABRADANT.